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ADN8831ACPZ-REEL7 Arkusz danych(PDF) 11 Page - Analog Devices |
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ADN8831ACPZ-REEL7 Arkusz danych(HTML) 11 Page - Analog Devices |
11 / 20 page Data Sheet ADN8831 Rev. A | Page 11 of 20 THEORY OF OPERATION The ADN8831 is a single chip TEC controller that sets and stabilizes a TEC temperature. A voltage applied to the input of the ADN8831 corresponds to a target TEC temperature setpoint (TEMPSET). By controlling an external FET H-bridge, the appropriate current is then applied to the TEC to pump heat either to or away from an object attached to the TEC. The objective temperature is measured with a thermal sensor attached to the TEC and the sensed temperature (voltage) is fed back to the ADN8831 to complete a closed thermal control loop of the TEC. For best stability, the thermal sensor is to be closed to the object. In most laser diode modules, a TEC and a NTC thermistor are already mounted in the same package to regulate the laser diode temperature. The ADN8831 integrates two self-correcting, auto-zero amplifiers (Chop1 and Chop2). The Chop1 amplifier usually takes a thermal sensor input and converts or regulates the input to a linear voltage output. The OUT1 (Pin 4) voltage is proportional to the object temperature. The OUT1 (Pin 4) voltage is fed into the compensation amplifier (Chop2) and compared with a tempera- ture setpoint voltage, creating an error voltage that is proportional to the difference. When using the Chop2 amplifier, a PID network is recommended, as shown in Figure 12. Adjusting the PID network optimizes the step response of the TEC control loop. A compromised settling time and the maximum current ringing become available when this is done. Details of how to adjust the compensation network are in the PID Compensation Amplifier (CHOP2) section. The TEC is differentially driven in an H-bridge configuration. The ADN8831 drives external MOSFET transistors to provide the TEC current. To further improve the power efficiency of the system, one side of the H-bridge uses a PWM driver. Only one inductor and one capacitor are required to filter out the switching frequency. The other side of the H-bridge uses linear output without requiring any additional circuitry. This proprietary configuration allows the ADN8831 to provide efficiency of >90%. For most applica- tions, a 4.7 μH inductor, a 22 μF capacitor, and a switching frequency of 1 MHz, maintain less than 0.5% worst-case output voltage ripple across a TEC. The maximum voltage across the TEC and current flowing through the TEC is to be set using the VLIM (Pin 31) and ILIMC (Pin 1)/ILIMH (Pin 32). Additional details are in the Maximum TEC Voltage Limit section and the Maximum TEC Current Limit section. PGND AGND TMPGD ITEC VTEC IN1N IN2P OUT1 IN1P ILIMH ILIMC VLIM AVDD VREF PVDD 5Ω LPGATE LFB LNGATE CS COMPSW SFB COMPOSC SPGATE SYNCI/SD SW SYNCO PHASE FREQ SS/SB SNGATE TEMP GOOD INDICATOR TEC CURRENT OUTPUT TEC VOLTAGE OUTPUT TEMPERATURE SET INPUT 30.1kΩ 10µF 27nF THERMISTOR 10kΩ 10kΩ 10kΩ 10kΩ 10kΩ 10kΩ 17.8kΩ 8.2kΩ 8.2kΩ IN2N OUT2 7.68kΩ 17.8kΩ 0.1µF 0.1µF 0.1µF VDD 3.0V TO 5.5V 0.1µF 40µF RSENSE 10kΩ 118kΩ 1kΩ 0.1µF 3.3µH 60µF VDD TEC NC NC NC = NO CONNECT Figure 12. Typical Application Circuit 1 |
Podobny numer części - ADN8831ACPZ-REEL7 |
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Podobny opis - ADN8831ACPZ-REEL7 |
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